Birthright citizenship just might be, former slaves believed, the safeguard they needed. In the decades before the Civil War, in an era when a remedy like the Fourteenth Amendment was hard to imagine, free black Americans embraced the view that they were citizens by virtue of having been born on U.S. soil. It was a lofty claim, especially because the Constitution was largely silent on the matter of who was a citizen and who was not. But for those who were descended from bondspeople, their circumstances were dire. Law and policy appeared to be conspiring against them, aimed directly at their tentative claims to belonging to the nation. Colonization societies organized to entice former slaves to migrate away, to Canada, the Caribbean, or Liberia in West Africa. Black laws restricted everyday life—work, travel, worship—to such a degree that black men and women felt squeezed out and many considered self-deportation.

In the U.S., birthright citizenship begins here, in the struggles of the marginalized and the despised to make this nation their own even as so many claimed that when it came to rights, it was a white man’s country. Most notorious among such denials of black citizenship was the U.S. Supreme Court’s 1857 decision in Scott v. Sandford, often referred to as the Dred Scott case. But African Americans saw Chief Justice Roger B. Taney and his decision coming from years away. They had encountered his view—that black people had no rights that white men were bound to respect—in Congress and state courts, in newspaper columns and political conventions. They denounced Taney and the high court, gathering in meeting halls and churches to decry the denial of their birthright. And they never deferred to it. Taney’s decision was another round in a struggle that would take them to the Civil War and beyond.

The 1868 ratification of the Fourteenth Amendment, especially its birthright-citizenship provision, was the culmination of a long struggle, rather than a newfangled postwar innovation. Black Americans had defined its necessity, set forth its terms, persisted even in the face of highly placed doubters, and then served up to the Reconstruction-era Congress an idea whose time had come. The Thirteenth Amendment made millions of enslaved people irretrievable and constitutionally free. But it was the Fourteenth Amendment that made them citizens, and with its ratification, the terms of citizenship were transformed for all those born in the U.S., setting in place a regime that persists until the present day. It is the very regime to which many Americans owe their sense of sureness when it comes to national belonging.

It might be easy to forget the origins of birthright citizenship. In many of our lives, it was conferred silently, without ceremony or much paperwork. We might assume it was always this way. It turns out that the quintessentially American story is not one about how it has always been this way. Instead, it is one about struggle—about how our democracy has been made to an important degree by people, like former slaves, who helped build the nation and asked in turn to be full members of it. It is a story about how people largely relegated to the margins make their way to the center—fitfully, unevenly, and not without opposition. Still, their striving, their quest, their insistence that citizenship is a two-way street and a bargain, rather than a gift or a privilege, is the legacy left to us by former slaves who saw themselves as belonging by virtue of birthright long before most others did.

In 2018, we find ourselves once again embroiled in a debate over citizenship, over who belongs, who is in and who is out. And the Fourteenth Amendment, a constitutional innovation that embraced former slaves as citizens, is now wielded by some as a weapon, held up as a barrier, and otherwise used to deny admission to those who have devoted lives and work to this nation, but always under a shroud of uncertainty. Some would undo the amendment’s birthright provision altogether, substituting for it regimes of blood—with belonging dependent upon who one’s parents were or were not—or of affirmation, in which only those willing to pledge themselves to the nation may join it.

What these proposals overlook is how firmly birthright citizenship is rooted in the heart of our democracy. Its purpose 150 years ago was to incorporate former slaves into the nation, regardless of their race or their status as one-time bondspeople. Birth was the great equalizer. And since its ratification, the amendment has served to gently arbitrate national belonging, ensuring that no arbitrary criteria—religion, race, descent, or political affiliation—can be wielded to deny citizenship. All those born here are citizens. And in a nation that has throughout its history struggled with recurring bouts of xenophobia, racism, bigotry, and more, these views have never determined who could be a citizen—even as they certainly shaped the quality of that citizenship for many Americans. As citizens, we are guaranteed a place, even as it has sometimes been a place to stay and to fight.

President Donald Trump, and legislators like Senator Lindsey Graham, have proposed changes to the birthright-citizenship regime. Likely such changes hinge on what is a phrase in the Fourteenth Amendment whose meaning is not clear on its face. Its authors carved out an exception to birthright for those said to be exempt from the jurisdiction of the United States. What did 19th-century lawmakers have in mind here? Certainly, they intended to exclude from birthright the children of foreign diplomats and occupying armies even when born in the U.S. Native Americans, members of their own sovereign nations, were also excluded. Some later claimed that this clause functioned to render the U.S.-born children of Chinese immigrants noncitizens. The U.S. Supreme Court said no in the 1898 case of U.S. v. Wong Kim Ark. Wong was a citizen, even as his parents were not. Today, the argument has been made that Wong’s case differed from that of today’s children of undocumented immigrants. There is no direct precedent here in U.S. law, and this tiny clause is where people like Trump and Graham may hang their hats.

Should either the president or Congress proceed with new interpretations of the Fourteenth Amendment, it will be left to the nation’s courts to resolve the constitutional questions that their novel interpretations of the amendment, or their wholesale abrogation of it, will present. When they do so, they must first take on history, a history in which a constitutional amendment was won by people whose often unrequited labor had built the nation. To limit or repeal the Fourteenth Amendment is to reject its democratic spirit, a spirit of expansive inclusion free of racism, anti-Semitism, political cronyism, or other narrowing prejudices. They will tell us that they possess, in a constitutional sense, the authority to do so, at will. The courts may affirm this. They may not. The lessons to be derived from the struggle black Americans waged 150 years ago concern their refusal to defer and an unwillingness to fold. Their ultimate victory came at great cost—the Civil War cost the United States three-quarters of a million lives, and almost its very existence. The victory they won was secured, in part, through the terms of the very Fourteenth Amendment that is under assault today. They would, I think, urge us to persist.

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Martha S. Jones is Society of Black Alumni Presidential Professor and Professor of History at Johns Hopkins University.